This invention relates generally to systems employing a charge coupled device (CCD) and particularly to a CCD system including a scanning or data transfer generator and method wherein the CCD is replaceable with a CCD having a different number of picture elements or pixels.
Charge coupled devices are finding use in a wide range of equipment requiring image sensing. For example, CCD image sensors can be used to replace the standard vidicon image pickup tubes which ordinarily are used in television cameras. An article, entitled "Charge-Coupled Devices Tackle TV Imaging," by Allan P. King and Michael Farrier which appeared in Electronic Design Aug. 6, 1981, Pages 183 through 190 explains how CCDs can be used in television cameras. The Model 80A Camera Controller and Model CH81A Camera Head available from Photometrics Ltd. of Tuscon, Ariz. also are examples of presently available equipment utilizing CCDs.
CCDs are used in conjunction with an optical lensing system which focuses the light from the object being investigated onto the CCD. Varying amounts of light on the individual pixels within the CCD cause electron generation within the pixels. The electron generation causes each pixel to develope a charge packet proportional to the incident light. The optical information from the object is, therefore, available in analog form across the pixels of the CCD array. The charge packets are then shifted out of the CCD and converted into digital form and stored in a digital memory where the various characteristics of the object can be checked or tested by the proper manipulation of the digital information.
CCDs are small, rugged devices having spacially precise sensing elements and, therefore, are advantageous for use in precise measuring systems. CCDs also are advantageous in imaging devices which develope an image by scanning. A CCD receives an image by the direct reception of light without the CCD being scanned. Accordingly, a CCD can image a scanned device without concern for the scanning rate of the device being imaged. For these reasons, CCDs are useful in testing color television kinescopes for blemishes and covergence and also for the inspection of geometric figures where high precision is required. The individual pixels within a CCD array typically are arranged horizontally in rows and vertically in columns whereby a given CCD imaging device provides a fixed number of pixels of information. As an example, the SID52501 CCD presently available from RCA has 320 vertical columns of pixels and 512 horizontal rows of pixels. Accordingly, the information is read out from the CCD and stored in 320 vertical columns and 512 horizontal rows of a digital memory. The technology of fabricating CCDs is rapidly expanding and CCDs having higher numbers of pixels are rapidly becoming available. With the present state of the art, the incorporation of a larger (or smaller) CCD into a particular system necessitates the redesign of the system because of the manner in which the analog data are read out from the CCD. Additionally, CCDs which are sensitive to a particular wavelength of energy, such as infrared, also are becoming available. A CCD sensitive to infrared energy typically requires transfer waveforms which are different from those required for a light sensitive CCD. It, therefore, would be highly advantageous to have a system which can receive a CCD having any number of horizontal rows and vertical columns of pixels, or which is responsive to a particular wavelength of light, without completely redesigning the system.
The instant invention fulfills these requirements by the provision of a CCD inspection system having a data transfer generator and a waveform memory wherein a CCD having any number of columns and rows of pixels can be insrted into the system by merely setting new horizontal and vertical scan numbers and new scanning waveforms into the system.